1. Field of the Invention
The present invention relates to a technique of estimating the time when a product composed of a plurality of parts fails and the degree of degradation of the parts, and reflecting them in maintenance planning.
2. Description of the Related Art
Conventional maintenance planning has depended on the experience and guesswork of servicemen. This has obstructed balancing the risk of user's loss due to the reason that products become unavailable and the cost of maintenance.
Specifically speaking, to reduce the risk of product failure, parts with high risk of failure are replaced before the end of the life, so that excessive replacement is carried out, increasing maintenance cost. In contrast, when products are used to the end of life so as to decrease the maintenance cost, servicemen have to make a visit after the products fail, thus increasing downtime to increase user's loss due to the reason that the products are unavailable. Consequently, the risk and the cost are in a trade-off relationship.
Some other business sectors adopt maintenance planning based on costs and risks. It is, however, difficult to estimate the costs when replacement parts (consumable parts) increase in number. In other words, at the time of determining if consumable parts should be replaced, it takes extremely high calculation cost to determine the best maintenance planning for the best combinations of consumable parts to be replaced. In addition, since it cannot be determined that how much the next visit time is delayed, the cost cannot be simply calculated.